Project Summary Abstract Due to our fragmented healthcare delivery system, sharing patient health information across healthcare delivery organizations is an essential component of high-quality care but does not occur routinely. When critical health information is missing, care continuity is impeded, with increased risk of poor patient outcomes. Older adults have a disproportionate share of complex health conditions that result in their needing to see multiple providers in different organizations. They are therefore at disproportionate risk of poor outcomes that result from lack of information sharing, including repeated testing and avoidable hospitalization. To improve information sharing across healthcare delivery organizations, there has been a substantial effort over the past eight years to promote adoption of electronic health records and the ability to share patient data between them (?health information exchange? or HIE). However, there is surprisingly little evidence about whether HIE is occurring in ways that will benefit older adults, both in terms of ensuring that the healthcare organizations that treat the same patient populations are able to engage in HIE with each other and, when they are, that they use HIE in ways that improve clinical outcomes (e.g., reduce repeat testing and hospitalization). Our project will provide a national picture of the extent to which healthcare delivery organizations that routinely treat the same older patients are able to share patient information electronically with each other. Today, no such measures exist, creating a problematic blindspot in terms of understanding whether there is connectivity where it is most needed. In addition, where healthcare delivery organizations are engaging in sharing patient information electronically, we will assess whether it is improving key outcomes for the older patients that receive care from those organizations. These outcomes include repeat testing, hospitalization and rehospitalization, and mortality. Importantly, we will assess whether the benefits from electronic information sharing disproportionately accrue to two populations of patients who are most at risk of poor outcomes from lack of information sharing: those with dementia and those with multiple health conditions. By focusing on these populations, we will be able to determine whether the current ?one-size-fits-all? approach to electronic health information sharing is working or whether it requires customization to the unique needs of different patient populations. By generating new evidence on the current state of electronic health information sharing across healthcare delivery organizations, study results will guide key stakeholders on how to combat the risks of care fragmentation by sharing information in ways that improve outcomes for older adults in general, and for the most vulnerable older adults in particular.